Water soluble silicone resin backcoat for thermal transfer ribbons

Abstract

A thermal transfer ribbon comprised of a flexible substrate, a thermal transfer layer on one surface of the substrate and a backcoat on the opposite surface of the substrate comprised of a water-soluble silicone block copolymer with blocks of silicone resin and water-soluble polymer.

What is claimed is:  
     
       1. A thermal transfer ribbon comprising a flexible substrate and a thermal transfer layer positioned on one surface of the flexible substrate and a backcoat positioned on the opposite surface comprising a water-soluble silicone block copolymer, wherein the water-soluble silicone block copolymer comprises silicone blocks of the formula                    
       wherein R, R′, R″ and R′″ are each, independently selected from the group consisting of H, OH, CH 3 , ethyl or propyl, 
       Q is the link to blocks of a water-soluble polymer, and  
       x and y are 1 or more.  
     
     
       2. A thermal transfer ribbon as in claim  1 , wherein the silicone block copolymer comprises blocks of water-soluble polymer selected from the group consisting of polyethylene oxide blocks, polypropylene oxide blocks and combinations thereof. 
     
     
       3. A thermal transfer ribbon as in claim  2 , wherein the polyethylene oxide blocks are of the formula 
       
         
           —(CH 2 ) 3 —(OCH 2 CH 2 ) z —OCH 3,    
         
       
       where Z is 1 to 100 and the polypropylene oxide blocks are of the formula 
       
         
           —(CH 2 ) 3 —(OCH 2 CH 2 CH 2 ) z —OCH 3,    
         
       
       wherein Z is 1 to 100. 
     
     
       4. A thermal transfer ribbon as in claim  1 , wherein the backcoating contains from 0.01 to 2 wt. % antifoaming agent based on the weight of water-soluble silicone block copolymer. 
     
     
       5. A thermal transfer ribbon as in claim  1 , wherein the backcoat is formed from an aqueous coating formulation comprising water, antifoaming agent and from 1 to 10 wt. % water-soluble silicone block copolymers applied to the substrate with a #0 Meyer rod. 
     
     
       6. A thermal transfer ribbon as in claim  5 , wherein the aqueous coating formulation is free of emulsifiers. 
     
     
       7. A thermal transfer ribbon as in claim  8  wherein the back coat is free of water soluble polymers other than water-soluble silicone block copolymers. 
     
     
       8. A thermal transfer ribbon as in claim  1 , wherein the backcoat is free of emulsifiers. 
     
     
       9. A thermal transfer ribbon comprising a flexible substrate and a thermal transfer layer positioned on one surface of the flexible substrate and a backcoat positioned on the opposite surface comprising a water-soluble silicone block copolymer having a weight average molecular weight of about 30,000. 
     
     
       10. A thermal transfer ribbon as in claim  5 , wherein the aqueous coating formulation is free of water-soluble polymers other than water-soluble silicone block copolymers. 
     
     
       11. A thermal transfer ribbon comprising a flexible substrate and a thermal transfer layer positioned on one surface of the flexible substrate and a back coat positioned on the opposite surface comprising a water-soluble silicone block copolymer comprising blocks of water-soluble polymers selected from the group consisting of polyethylene oxide blocks polypropylene oxide blocks and combinations thereof, wherein the water-soluble polymer blocks comprise at least 50 wt. % of the silicone block copolymer. 
     
     
       12. A thermal transfer ribbon as in claim  11 , wherein the water-soluble polymer blocks comprise 50%-60% propylene oxide blocks and 40%-50% ethylene oxide blocks.